This invention relates to filtration processes and equipment, and more particularly to horizontal belt filter apparatus, particularly for use in minerals processing.
FIGS. 1, 2, and 4 show a horizontal belt filter 900 having a conventional vacuum pan assembly 990. Horizontal belt filter 900 comprises a frame 930, a plurality of return rollers 920 and a drainage belt 910 having a number of pores 912 provided therein which are configured to pass fluid and moisture from a slurry (not shown) to the conventional vacuum pan assembly 990 positioned below the belt 910. Belt 910 supports filter media 914 such as a filter cloth. Conventional vacuum pan assembly 990 comprises a swing arm 940 which is pivotally attached to said frame 930 by way of a pivot bracket 941 having a first pivot member 946, and a second pivot member 936 provided to the frame 930. A vacuum pan 950 having an elongated inlet 951 and a channel 952 is mounted to the swing arm 940 via a number of fasteners 953 passing through at least one mount 957 on the pan 150. A wear plate 959 having a number of apertures 955 may serve as a sacrificial interface between the pan 150 and the belt 910. Apertures 955 in the wear plate 959 allow fluid and moisture from slurry passing through pores 912 to enter the conventional vacuum pan assembly 990 positioned below the belt 910. A first securing portion 944 is provided to a distal end of the swing arm 940, opposite the pivot bracket 941 and the first pivot member 946. The first securing portion 944 is configured to mate with a complementary second securing portion (not shown) provided at a predetermined location on the frame 930 of the filter 900. Engagement between the first securing portion 944 and the second securing portion (not shown) serves to keep vacuum pan 950 and wear plate 959 in close communication with belt 910.
As best shown in FIGS. 2 and 3, at least one shim 960 is typically placed between the swing arm 940 and mount 957 to better align the inlet 951 of the pan 950 with the pores 912 in the belt 910 and sometimes to adjust the tilt of the pan 950 to match an inclination of the belt 910. The exact number and/or configuration of shims 960 may vary between each swing arm 940 and mount 957 along the length of the filter 900, and will frequently change as portions of wear plate 959 dimensionally change (e.g., in thickness) due to continued friction with the belt 910.
A significant disadvantage of using shims 960 is that when used wear plates 959 are replaced with thicker new wear plates (or when any portion of the conventional vacuum pan assembly 990 such as the pan 950 itself needs to be removed for routine maintenance or cleaning), there is no simple way to restore the position of the pan 950 to a “factory default” alignment configuration with respect to the swing arm 940. In other words, shims 960 necessary for use with thin worn wear plates 959, which are removed from the assembly 990 to accommodate thick new wear plates 959, will need to be replaced in a new configuration in a lesser number in order to bring the pan 950 into proper re-alignment with the belt 910. Such re-configuring and adjustment steps require unnecessary downtime and labor.
To add to the abovementioned problem, shims are typically custom-fabricated at each shim location. Multiple shims of varying thickness are required at each shim point to achieve the desired elevation required for belt-to-pan alignment and proper vacuum seal between the belt 910 and vacuum pan assembly 990. Shims 960 are frequently lost, mixed up or accidentally confused with other shims 960, and additional shims 960 may need to be quickly fabricated and provided in the field in order to adjust the positioning of the vacuum pan 950 during routine maintenance.
Jack screws often “seize” in place after a short time in operation, thereby resulting in the inability to adjust the elevation or removal of vacuum pan 950 during routine maintenance. Neither shims 960 or jack screws (not shown) provide a quick and efficient way to re-establish “factory-set elevation points” for a vacuum pan 950 after maintenance adjustments are performed.
Conventionally, the horizontal adjustment of vacuum pans 950 typically involves welding an adjusting plate (not shown) to the swing arm in-situ during assembly. As a result of in-situ welding, additional cleaning of the weld area and protective repainting is required. These extra steps add to the total commissioning time and cost. Moreover, welding exposes expensive components (e.g., belt 910) to potential damage.